The technique of cutting grooves in concrete to allow for expansion is well known. This has long been performed using high powered concrete saws. Only recently has this technique been applied to concrete coated pipe.
It is necessary to apply a high density concrete aggregate coating to pipe used in marine applications for antibuoyancy purposes. The concrete coating is normally several inches in thickness and is applied over an anti-corrosion protective coating. With the laying of pipe in deeper and deeper waters heretofore unknown problems have been encountered. Two problems in particular have evolved. One, the inability of the pipe to meet the greatly increased bending radius at the greater depths may result in buckling of the pipes requiring time consuming and costly procedures to remove the damaged joint. Second, even if the pipe does not buckle under the sharply increased bending radius, the concrete coating can "jump off" the pipe as the stress forces increase.
In order to overcome or at least reduce the possibility of the two foregoing problems it has become a requirement in certain instances to require heavy steel rod reinforcing in the concrete coating to strengthen it and reduce the possibility of the concrete jumping off the pipe. In addition, it is required that circumferential grooves be cut in the concrete coating at spaced intervals along the length of the pipe so as to permit a greater flexure of the pipe as it encounters the extreme bending radius necessary for a deep lay operation thus reducing the possibility of the pipe buckling under stress.